Speed-changing mechanism.



P'ATENTED JUNE 25, 1907.

0.1. REED? SPEED CHANGING MECHANISM.

APPLICATION FILED FEB. 23, 1906.

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UNITED STATES PATET @FFIQE.

SPEED-CHANGING MECHANISM.

Specification of Letters Patent.

Patented June 25, 1907.

Application filed February 23,1905. Serial No. 24:6,964.

'1'0 alt whom, zit may concern:

Be it known that I, CHARLES J. REED, a citizen of the United States,residing at Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented certain new and useful Improvements inSpeed- Changing Mechanism, of which the following is a specification.

In U. S. Patent 758,561,granted to me April 26, 1904, I have shown aspeed-changing mechanism comprising an expansible double pulley placedbetween and belted to pulleys on the driving and driven shafts. Theexpansible pulley is carried by a shaft journaled in the ends of armswhich are fixed on a rockshaft. When the rim-sections of the expansiblepulley are shifted to vary the speed of the driven shaft, this pulleyrocks to compensate for the corresponding changes in the working lengthsof the belts by which it receives and transmits power. As the pulleyrocks, its center of gravity shifts to one side or the other of its lineof support and the horizontal component of its unbalanced weight isadded to the normal tension of one belt and subtracted from that of theother. The friction of the belts on the pulleys is therebyrendered-unequal and the belts are unduly stretched.

The present invention is a means for counterbalancing the weight of anexpansible pulley as it rocks during adjustment. The preferred means isa spring which engages the rock-shaft carrying the pulley-supportingarms and acts in oppositionto the force of gravity on the pulley.

Referring to the accompanying drawings, Figure 1 is an end elevation ofa driving and driven pulley and an intermediate expansible pulley beltedthereto; Fig. 2 is a side elevation of the rockshaft and arms whichcarry the expansible pulley and of a straight counterbalancing spring;Fig. 2 is a detail end view of the spring-engaging collar shown in Fig.2; Fig. 3 is a side elevation of a rockshaft controlled by two coiledsprings Fig. 4-

is a side elevation of a rockshaft having depending arms to carry thepulley and cams which receive the pressure of a straight spring; andFig. 1* is a detail end view of one of the cams shown in Fig. 4c.

Referring to Fig. 1, the driving pulley 1 and driven pulley 2 areconnected to the two drums of the intermediate pulley 3 by the belts 4,5, respectively. The double pulley is carried by a shaft journaled inbearings at the upper ends of rock-arms 6, which are fixed on arockshaft 7 journaled in bearings 8. The expansible pulley 3 may be ofany well-known construction, comprising plural sets of rim-sectionswhich are shifted to and from the axis by suitable adjusting means. Asthe rim-sections of one drum are adjusted outward and those of the otherdrum inward, the working lengths of the belts 4, 5 correspondinglychange and the expansible pulley rocks on the shaft 7, thereby shiftingits center of gravity to one side of the lineof support. In the positionshown in Fig. 1', the horizontal component of the weight of theexpansible pulley and its support-arms tends to increase the tension ofthe belt 5 and decrease that of the belt 4.

Referring to Fig. 2, a spring 9 consisting of a steel rod extendsbetween and is entered at its ends in the bearings 8, beneath andparallel to the rockshaft. Adjustably secured on the rockshaftintermediate its bearings is a collar 10 having downwardly-projectinglugs 11 which engage the spring-rod. As the expansible pulley tilts ineither direction to one side of. the axis of its rockshaft, the spring 9tends to restore it to a central position, the force of the spring beingredetermined to compensate for the unba anced weight of the pulley.

In Fig. 3, short spiral springs 12 are shown surrounding the rockshaft7, one end of each spring being secured to the shaft and the other endto a bearing 8. These coiled springs normally hold the rock-arms in avertical position.

Fig. 4 illustratesa spring-mechanism for counterbalancing the weight ofa pulley which is hung in depending rock-arms 6". A straight spring-rod13, like that shown in Fig. 2, extends between and is held at its endsby the bearings 8. Adjustably secured upon the rockshaft near its middleare two rings 14 having cams 15 which bear against antifriction rollers16 loosely carried by therod 13. The shape of the cams and the force ofthe spring 13 are predetermined in accordance with the weight of thepulley to be counterbalanced. The pressure of the spring on the cams mayalso be varied by adjusting the cams to or from each other on therockshaft.

I claim In a speed-changing mechanism, an ex- IIO pansible pulley havingplural drums, a rockshaft having arms carrying said pulley,ournal-bearings at the ends of said shaft, and a spring engaging saidshaft between said bearings and arranged to counterbalance the weight ofsaid pulley as it rocks in either direction, as set forth.

In testimony whereof, I afliX my signature in presence of two witnesses.

CHARLES J. REED.

Witnesses:

H. W. ROGERS, J. W. RITTER.

